In U.S. Pat. No. 5,439,209 to Kurt Runzi a paper stacking apparatus is disclosed which is capable of separating successive documents or jobs on the stack being formed. The apparatus has a conveyor belt for transporting the individual sheets to a stacker. A holder is arranged above the conveyor belt. The holder holds a row of freely rotatable balls which press the sheets onto the belt. On one side of the belt a guide rail is arranged which is pivotable about its rear end between two pivot positions. In both positions the belt converges towards the guide rail in the transport direction. The guide rail is switched to its other position each time the last page of a document printed has passed the conveyor. Thereby, the documents are separated from one another on the stack being formed by a lateral shift. This way the individual documents can easily be separated from one another in a following operation. Presently, this separation is performed manually. This U.S. patent is declared an integral part of the present application.
In modern high speed printing machines, e.g. laser printers, the individual papers of the successive documents or jobs are printed in successive order of their page number and outputted with their printed side down. The printed papers are stacked in a stacker. The sheets of the individual documents are then in correct order.